Semiconductor module and semiconductor device

ABSTRACT

A semiconductor module includes first and second semiconductor elements connected in series, an insulating substrate, first and second metal patterns formed on a first main surface and a second main surface of the insulating substrate, and first, second, and third electrode plates. A lower surface electrode and an upper surface electrode of the first semiconductor element are bonded to the first metal pattern and the first electrode plate, respectively. The first metal pattern and the third electrode plate are bonded together. An upper surface electrode of the second semiconductor element is bonded to the third electrode plate. A lower surface electrode of the second semiconductor element is electrically connected to the second metal pattern. The second metal pattern and the second electrode plate are bonded together. One end of the first electrode plate and one end of the second electrode plate are led out on the same side.

FIELD OF THE INVENTION

The present invention relates to a semiconductor module and asemiconductor device. For example, the present invention relates to asemiconductor module for electric power use that handles a largecurrent.

DESCRIPTION OF THE BACKGROUND ART

In recent years, there has been a trend toward larger-capacitysemiconductor modules for electric power use. A large-capacitysemiconductor module has increased parasitic inductance because of itslong wiring length. The operation of the semiconductor module at a highswitching speed with a low switching loss results in an increase insurge voltage. Therefore, there has been a demand for low-inductancesemiconductor modules. According to the Japanese Patent ApplicationLaid-Open No. 2013-45974, one insulating substrate is overlaid onanother insulating substrate to provide the parallel current paths,thereby reducing inductance.

In general, for the working of the semiconductor module for power use,the P electrode and the N electrode are desirably led out from thepackage in the same direction. According to the Japanese PatentApplication Laid-Open No. 2013-45974, the N side (GND) is locatedimmediately above the heat sink such that the P electrode and the Nelectrode are aligned. The wiring of the upper arm and the AC electrodebeing at the same potential include a plurality of components.Similarly, the wiring of the lower arm and the N electrode being at thesame potential include a plurality of components.

Along with an increase in the number of components of the semiconductormodule, the number of manufacturing process increases, deteriorating theassembly performance. In particular, the technique has beenunfortunately unsuitable for application to a large-capacity productincluding a plurality of parallel arrangements of semiconductorelements. In addition, the double-layer structure of insulatingsubstrates has deteriorated the heat dispersion properties.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor moduleand a semiconductor device having low inductance as well as improvedassembly performance and improved heat dispersion properties.

A semiconductor module according to the present invention includes afirst semiconductor element and a second semiconductor conductor elementconnected in series, an insulating substrate, a first metal patternformed on a first main surface of the insulating substrate, a secondmetal pattern formed on a second main surface side of the insulatingsubstrate, a first electrode plate, a second electrode plate, and athird electrode plate. The first and second semiconductor elements eachinclude an upper surface electrode and a lower surface electrode. Thelower surface electrode of the first semiconductor element is bonded tothe first metal pattern. The upper surface electrode of the firstsemiconductor element is bonded to the first electrode plate. The firstmetal pattern and the third electrode plate are bonded to each other.The upper surface electrode of the second semiconductor element isbonded to the third electrode plate. The lower surface electrode of thesecond semiconductor element is electrically connected to the secondmetal pattern. The second metal pattern and the second electrode plateare bonded to each other. One end of the first electrode plate and oneend of the second electrode plate are led out on the same side.

In the semiconductor module according to the present invention, thewiring of the AC electrode and the wiring of the N electrode can beformed as the single third electrode plate and the single firstelectrode plate, respectively. Consequently, the wiring of the ACelectrode and the wiring of the N electrode can be shortened andsimplified. This reduces the number of components of the semiconductormodule. The first and third electrode plates are directly bonded to thesemiconductor elements without a member such as a wire locatedtherebetween, so that the throughput of the manufacturing process can beimproved. Unlike the wiring by wire bonding, this approach contributesto the improvement of assembly performance. The wiring formed of thefirst, second, and third electrode plates reduces the wiring resistance,being little affected by heating caused by Joule heat. In addition, itis expected that the first, second, and third electrode plates dissipateheat. This contributes to the reduced thermal resistance. The firstelectrode plate and the second metal pattern that is in connection withthe second electrode plate are wired in parallel with each other. Thiscan further reduce the inductance between the P electrode and the Nelectrode.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor module according toa first preferred embodiment;

FIG. 2 is a plan view of the semiconductor module according to the firstpreferred embodiment;

FIG. 3 is a connecting diagram of the semiconductor module according tothe first preferred embodiment;

FIG. 4 is a connecting diagram of the semiconductor device according tothe first preferred embodiment;

FIG. 5 is a cross-sectional view of a semiconductor module according toa second preferred embodiment; and

FIG. 6 is a cross-sectional view of a semiconductor module according toa third preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Preferred Embodiment>

FIGS. 1 and 2 are a cross-sectional view and a plan view of asemiconductor module 100 according to a first preferred embodiment. FIG.3 is a connecting diagram of the semiconductor module 100.

As shown in FIG. 1, the semiconductor module 100 includes first andsecond semiconductor elements 13 and 11 serving as switching elements,an insulating substrate (a first ceramic substrate 5), a first metalpattern 8 formed on a first main surface (upper surface) of theinsulating substrate (the first ceramic substrate 5), and a second metalpattern 9 formed on a second main surface (lower surface) of theinsulating substrate (the first ceramic substrate 5).

The semiconductor module 100 further includes a first electrode plate 2corresponding to the N electrode, a second electrode plate 1corresponding to the P electrode, and a third electrode plate 3corresponding to the AC electrode.

The semiconductor module 100 further includes a third metal pattern 7formed on the first main surface of the insulating substrate (the firstceramic substrate 5) separately from the first metal pattern 8.

The semiconductor module 100 further includes a second ceramic substrate6 and a heat sink 10 located on the back surface of the second ceramicsubstrate 6. The heat sink 10 includes a plurality of fins 10 a.

The semiconductor module 100 further includes a first freewheeling diode14 connected in parallel with the first semiconductor element 13 and asecond freewheeling diode 12 connected in parallel with the secondsemiconductor element 11.

The first and third metal patterns 7 and 8 are formed on the uppersurface of the first ceramic substrate 5. The second metal pattern 9 isformed on the upper surface the second ceramic substrate 6. The heatsink 10 is located on the lower surface of the second ceramic substrate6.

In the first preferred embodiment, for example, each of the firstsemiconductor element 13 and the second semiconductor element 11 is aninsulated gate bipolar transistor (IGBT). Each of the first and secondsemiconductor elements 13 and 11 is, for example, a wide bandgapsemiconductor element (such as a silicon carbide (SiC) semiconductorelement and a gallium nitride (GaN) semiconductor element). The firstand second semiconductor elements 13 and 11 each include an uppersurface electrode and a lower surface electrode being the mainelectrodes. The first and second freewheeling diodes 14 and 12 eachinclude an upper surface electrode and a lower surface electrode.

As shown in FIG. 1, the lower surface electrode of the firstsemiconductor element 13 and the lower surface electrode of the firstfreewheeling diode 14 are bonded to the first metal pattern 8 throughsolder 19 and solder 21, respectively. The upper surface electrode ofthe first semiconductor element 13 and the upper surface electrode ofthe first freewheeling diode 14 are bonded to the first electrode plate2 through solder 20 and solder 22, respectively.

The first metal pattern 8 and the third electrode plate 3 are bondedtogether through, for example, solder. The upper surface electrode ofthe second semiconductor element 11 and the upper surface electrode ofthe second freewheeling diode 12 are bonded to the third electrode plate3 through solder 16 and solder 18, respectively.

The lower surface electrode of the second semiconductor element 11 andthe lower surface electrode of the second freewheeling diode 12 arebonded to the third metal pattern 7 through solder 15 and solder 17,respectively.

The third metal pattern 7 and the second metal pattern 9 areelectrically connected to each other through a metal member 4 having aplate shape. The second metal pattern 9 and the second electrode plate 1are bonded together through, for example, solder.

One end of the first electrode plate 2 and one end of the secondelectrode plate 1 are led out on the same side of the case (a case 24b). One end of the third electrode plate 3 is led out on a case 24 a.

The electrode plates and the metal patterns (such as the secondelectrode 1 and the third metal pattern 7) are not necessarily bonded toeach other by soldering and may be, for example, directly bondedtogether by ultrasonic waves.

Similarly, the electrodes of the semiconductor elements and theelectrodes of the freewheeling diodes are bonded to the metal patternsor the electrode plates by soldering. Alternatively, for example, theymay be directly bonded together by ultrasonic waves.

As shown in FIGS. 1 and 2, the semiconductor module 100 according to thefirst preferred embodiment has the “2 in 1” structure in which anupper-arm semiconductor element and a lower-arm semiconductor elementare included in a case. The first electrode plate 3 serving as the ACelectrode and the first metal pattern 8 are at the same potential. Thefirst electrode plate 2 serving as the N electrode and the GND are atthe same potential. The second electrode plate 1 serving as the Pelectrode, the second metal pattern 9, the metal member 4, and the thirdmetal pattern 7 are at the same potential.

A case 24 houses: the first and second semiconductor elements 13 and 11;the first and second freewheeling diodes 14 and 12; the first, second,and third electrode plates 2, 1, and 3; and the first, second, and thirdmetal patterns 8, 9, and 7. The inside of the case 24 is sealed with gel23. The gel 23 may be resin.

FIG. 4 is a connecting diagram of the semiconductor device according tothe first preferred embodiment. The semiconductor device according tothe first preferred embodiment has a configuration in which threesemiconductor modules 100 are housed in the case. For example, thesemiconductor device having the “6 in 1” structure as shown in FIG. 4can be used to drive the three-phase motor.

<Effects>

The semiconductor module 100 according to the first preferred embodimentincludes the first and second semiconductor elements 13 and 11 connectedin series, the insulating substrate (the first ceramic substrate 5), thefirst metal pattern 8 formed on the first main surface of the insulatingsubstrate, the second metal pattern 9 formed on the second main surfaceside of the insulating substrate, the first electrode plate 2, thesecond electrode plate 1, and the third electrode plate 3. The first andsecond semiconductor elements 13 and 11 each include an upper surfaceelectrode and a lower surface electrode. The lower surface electrode ofthe first semiconductor element 13 is bonded to the first metal pattern8. The upper electrode of the first semiconductor element 13 is bondedto the first electrode plate 2. The first metal pattern 8 and the thirdelectrode plate 3 are bonded together. The upper surface electrode ofthe second semiconductor element 11 is bonded to the third electrodeplate 3. The lower surface electrode of the second semiconductor element11 is electrically connected to the second metal pattern 9. The secondmetal pattern 9 and the second electrode plate 1 are bonded together.One end of the first electrode plate 2 and one end of the secondelectrode plate 1 are led out on the same side.

As shown in FIG. 1, in the semiconductor module 100 according to thefirst preferred embodiment, the P electrode is wired on the second metalpattern 9 on the second main surface of the first ceramic substrate 5,so that the wiring of the AC electrode and the wiring of the Nelectrodes can be formed as the single third electrode plate 3 and thesingle first electrode plate 2, respectively. Consequently, the wiringof the AC electrode and the wiring of the N electrode can be shortenedand simplified. This reduces the number of components of thesemiconductor module 100.

The first and third electrode plates 2 and 3 are directly bonded to thesemiconductor elements without a member such as a wire locatedtherebetween, so that the throughput of the manufacturing process can beimproved. Unlike the wiring by wire bonding, this approach contributesto the improvement of assembly performance.

In general, the wiring through wire connection is disadvantageous inthat the increased interconnection resistance evolves Joule heat,causing heating of the wiring. In the first preferred embodiment, thewiring formed of the first, second, and third electrode plates 2, 1, and3 reduces the wiring resistance, being little affected by heating causedby Joule heat. In addition, it is expected that the first, second, andthird electrode plates 2, 1, and 3 dissipate heat. This contributes tothe reduced thermal resistance, which has been a challenge.

In the first preferred embodiment, the first electrode plate 2 and thesecond metal pattern 9 that is in connection with the second electrodeplate 1 are wired in parallel with each other. This can further reducethe inductance between the P electrode and the N electrode.

The use of the P electrode having a large wiring length extends theoverall current path between the P electrode and the N electrode. In thefirst preferred embodiment, the electrode is wired as the electrodeplate, thereby reducing Joule heat and the inductance between theremaining electrodes.

The structure above including the third electrode plate 3 as the ACelectrode and the first electrode plate 2 as the N electrode facilitatesthe wiring work in the manufacturing process. This structure istherefore capable of readily providing a large-capacity module withchips connected in parallel. This structure, which reduces thermalresistance, size, and induction and improves assembly performance, isbest suited to the module to be subjected to a large current.

The semiconductor module 100 according to the first preferred embodimentfurther includes the third metal pattern 7 formed on the first mainsurface of the insulating substrate (the first ceramic substrate 5)separately from the first metal pattern 8. The lower surface electrodeof the second semiconductor element 11 is bonded to the third metalpattern 7, so that the third metal pattern 7 and the second metalpattern 9 are electrically connected to each other.

The third metal pattern 7 is located on the first main surface of thefirst ceramic substrate 5, so that the third metal pattern 7 is bondedto the lower electrode of the second semiconductor element 11 and thethird metal pattern 7 is electrically connected to the second metalpattern 9. This configuration allows the lower surface electrode of thesecond semiconductor element 11 and the second metal pattern 9 to beelectrically connected to each other.

The semiconductor module 100 according to the first preferred embodimentfurther includes the first freewheeling diode 14 connected in parallelwith the first semiconductor element 13 serving as a switching elementand the second freewheeling diode 12 connected in parallel with thesecond semiconductor element 11 serving as a switching element. Thefirst and second freewheeling diodes 14 and 12 each include an uppersurface electrode and a lower surface electrode. The lower surfaceelectrode of the first freewheeling diode 14 is bonded to the firstmetal pattern 8. The upper surface electrode of the first freewheelingdiode 14 is bonded to the first electrode plate 2. The upper surfaceelectrode of the second freewheeling diode 12 is bonded to the thirdelectrode plate 3. The lower surface electrode of the secondfreewheeling diode 12 is electrically connected with the second metalpattern 9.

Thus, the first and second semiconductor elements 13 and 11 being, forexample, IGBTs are protected from a surge current in the semiconductormodule 100 including the freewheeling diodes connected in parallel withthe respective IGBTs.

The semiconductor device according to the first preferred embodimentincludes the plurality of semiconductor modules 100 and the case. Thecase houses the plurality of semiconductor modules 100 connected inparallel.

For example, the “6 in 1” structure in which three semiconductor modules100 in parallel are housed in the case provides the inverter for drivingthe three-phase motor. The plurality of semiconductor modules 100 arehoused in the case, so that the semiconductor device can be reduced insize and the productivity can be improved.

The semiconductor module 100 according to the first preferred embodimentfurther includes the heat sink 10 held below the surface of the secondmetal pattern 9 opposite to the insulating substrate (the first ceramicsubstrate 5) with the insulating material (the second ceramic substrate6) located therebetween.

The semiconductor modules 100 including the heat sink 10 combinedtherewith has further improved heat dispersion properties.

The first and second semiconductor elements 13 and 11 of thesemiconductor module 100 according to the first preferred embodiment arewide bandgap semiconductor elements.

The wide bandgap semiconductors made of, for example, SiC and GaN, whichare driven at a high carrier frequency on the application, serve thepurpose of reducing power loss. Even when being driven at a high carrierfrequency, the semiconductor module 100 having the low-inductancestructure is capable of reducing the surge voltage. Thus, it isparticularly advantageous to apply the wide bandgap semiconductor to thesemiconductor module 100.

<Second Preferred Embodiment>

FIG. 5 is a cross-sectional view of a semiconductor module 200 accordingto a second preferred embodiment. The semiconductor module 200 accordingto the second preferred embodiment has the configuration in which themetal member 4 included in the semiconductor module 100 is eliminatedand the second metal pattern 9 and the third metal pattern 7 areintegrally bonded through a junction 25. The configuration except forthe above is the same as that of the first preferred embodiment, and adescription thereof is omitted.

The second metal pattern 9 and the third metal pattern 7, which arebonded together on the outer side of the periphery of the first ceramicsubstrate 5 in FIG. 5, may be bonded together via a through-hole in thefirst ceramic substrate 5.

<Effects>

The semiconductor module 200 according to the second preferredembodiment further includes the third metal pattern 7 formed on thefirst main surface of the insulating substrate (the first ceramicsubstrate 5) separately from the first metal pattern 8. The lowersurface electrode of the second semiconductor element 11 is bonded tothe third metal pattern 7. The third metal pattern 7 and second metalpattern 9 are made of the same material. The third metal pattern 7 andthe second metal pattern 9 are integrally bonded.

Thus, the second preferred embodiment eliminates the metal member 4included in the first preferred embodiment. This configuration canfurther reduce the number of components of the semiconductor module 200.

<Third Preferred Embodiment>

FIG. 6 is a cross-sectional view of a semiconductor module 300 accordingto a third preferred embodiment. In the semiconductor module 100, thelower surface electrode of the second semiconductor element 11 and thelower surface electrode of the second freewheeling diode 12 are bondedto the third metal pattern 7. Meanwhile, in the semiconductor module 300according to the third preferred embodiment, which eliminates the thirdmetal pattern 7, the lower surface electrode of the second semiconductorelement 11 and the lower surface electrode of the second freewheelingdiode 12 are bonded to the second metal pattern 9.

As shown in FIG. 6, in the third preferred embodiment, the second metalpattern 9 includes an extending region 9 a that does not overlap theinsulating substrate (a first ceramic substrate 5 a) in plan view. Thelower surface electrode of the second semiconductor element 11 is bondedto the extending region 9 a of the second metal pattern 9 through thesolder 15. The configuration except for the above is the same as that ofthe first preferred embodiment, and a description thereof is omitted.

<Effects>

In the semiconductor module 300 according to the third preferredembodiment, the second metal patter 9 includes the extending region 9 athat does not overlap the insulating substrate (the first ceramicsubstrate 5 a) in plan view. The lower surface electrode of the secondsemiconductor element 11 is bonded to the extending region 9 a of thesecond metal pattern 9.

The third preferred embodiment includes the first ceramic substrate 5 aobtained by downsizing the first ceramic substrate 5 included in thefirst preferred embodiment and eliminates the third metal pattern 7 thathas been originally formed in the region devoid of the first ceramicsubstrate 5 due to the downsizing. This configuration reduces the regionin which two substrates being the first and second ceramic substrates 5a and 6 overlap each other, translating into the improvement of thermalresistance. In addition, this configuration reduces the number ofcomponents of the semiconductor module 300.

In the third preferred embodiment, inductance can be reduced althoughthe coupling region for coupling the P electrode and the N electrodedecreases. The semiconductor module 300 according to the third preferredembodiment is capable of achieving low inductance and low thermalresistance and is therefore particularly effective when being appliedto, for example, a step-up converter having a higher carrier frequencyin which the lower arm works in severer conditions.

In the present invention, the above preferred embodiments can bearbitrarily combined, or each preferred embodiment can be appropriatelyvaried or omitted within the scope of the invention.

While the invention has been shown and described in detail, theforegoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

What is claimed is:
 1. A semiconductor module comprising: a firstsemiconductor element and a second semiconductor element connected inseries; an insulating substrate; a first metal pattern formed on a firstmain surface of said insulating substrate; a second metal pattern formedon a second main surface side of said insulating substrate; a firstelectrode plate; a second electrode plate; and a third electrode plate,wherein said first and second semiconductor elements each include anupper surface electrode and a lower surface electrode, said lowersurface electrode of said first semiconductor element is bonded to saidfirst metal pattern, said upper surface electrode of said firstsemiconductor element is bonded to said first electrode plate, saidfirst metal pattern and said third electrode plate are bonded to eachother, said upper surface electrode of said second semiconductor elementis bonded to said third electrode plate, said lower surface electrode ofsaid second semiconductor element is electrically connected to saidsecond metal pattern, said second metal pattern and said secondelectrode plate are bonded to each other, and one end of said firstelectrode plate and one end of said second electrode plate are led outon the same side.
 2. The semiconductor module according to claim 1,further comprising a third metal pattern formed on the first mainsurface of said insulating substrate separately from said first metalpattern, wherein said lower surface electrode of said secondsemiconductor element is bonded to said third metal pattern, and saidthird metal pattern and said second metal pattern are electricallyconnected to each other.
 3. The semiconductor module according to claim1, further comprising a third metal pattern formed on the first mainsurface of said insulating substrate separately from said first metalpattern, wherein said lower surface electrode of said secondsemiconductor element is bonded to said third metal pattern, said thirdmetal pattern and said second metal pattern are made of the samematerial, and said third metal pattern and said second metal pattern areintegrally bonded.
 4. The semiconductor module according to claim 1,wherein said second metal pattern includes an extending region that doesnot overlap said insulating substrate in plan view; and said lowersurface electrode of said second semiconductor element is bonded to saidextending region of said second metal pattern.
 5. The semiconductormodule according to claim 1, further comprising: a first freewheelingdiode connected in parallel with said first semiconductor elementserving as a switching element; and a second freewheeling diodeconnected in parallel with said second semiconductor element serving asa switching element, wherein said first and second freewheeling diodeseach include an upper surface electrode and a lower surface electrode,said lower surface electrode of said first freewheeling diode is bondedto said first metal pattern, said upper surface electrode of said firstfreewheeling diode is bonded to said first electrode plate, said uppersurface electrode of said second freewheeling diode is bonded to saidthird electrode plate, and said lower surface electrode of said secondfreewheeling diode is electrically connected to said second metalpattern.
 6. A semiconductor device comprising: a plurality of saidsemiconductor modules according to claim 1; and a case, wherein saidplurality of semiconductor modules are connected in parallel and housedin said case.
 7. The semiconductor module according to claim 1, furthercomprising a heat sink held below a surface of said second metal patternopposite to said insulating substrate with an insulating materiallocated therebetween.
 8. The semiconductor module according to claim 1,wherein said first and second semiconductor elements comprise widebandgap semiconductor elements.